Method of making alcohols

ABSTRACT

Methods and systems for the synthesis of alcohol are described herein. The methods and systems incorporate the novel use of a high shear device to promote dispersion and solubility of olefins in water. The high shear device may allow for lower reaction temperatures and pressures and may also reduce reaction time. In an embodiment, a method of making an alcohol comprises introducing an olefin into a water stream to form a gas-liquid stream. The method further comprises flowing the gas-liquid stream through a high shear device so as to form a dispersion with gas bubbles having a mean diameter less than about 1 micron. In addition, the method comprises contacting the gas-liquid stream with a catalyst in a reactor to hydrate the olefin gas and form an alcohol.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patent application Ser. No. 12/335,270, filed Dec. 15, 2008, which is a divisional application of U.S. patent application Ser. No. 12/143,200, filed Jun. 20, 2008, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 60/946,499 and U.S. Provisional Patent Application No. 60/946,465, filed Jun. 27, 2007. The disclosures of said applications are hereby incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

TECHNICAL FIELD

This invention relates generally to the field of chemical reactions. More specifically, the invention relates to methods of synthesizing alcohols incorporating high shear.

BACKGROUND OF THE INVENTION

A process for hydrating an olefin, especially a lower olefin such as ethylene, propylene or butene, to prepare a corresponding alcohol such as ethanol, propanol or butanol, is industrially important as alcohol has applications in many areas of industry, science, medicine, and technology. In light of the recent developments in using ethanol as a fuel source, improved processes for producing alcohol has become even more desirable Various processes are known for the alcohol hydration reaction, but using a mineral acid such as sulfuric acid or phosphoric acid as a catalyst has been the most prevalent industrial method of production. In addition, isopropanol (isopropyl alcohol) is widely used today as a solvent, disinfectant and fuel additive. In the chemical industry it is a very useful intermediate in organic synthesis.

Typically, alcohols such as ethanol or isopropanol may be produced by hydrating olefins using a phosphoric acid supported on a silica gel. In this process, however, phosphoric acid supported on the silica gel may be eluted causing degradation of catalyst activity. Accordingly, it is necessary to perpetually add phosphoric acid. Therefore, problems arise in connection with the treatment of the discharged waste liquid and the corrosion of the material of equipment. Furthermore, a large quantity of energy is necessary for recovery of unreacted ethylene or separation and purification of the produced ethanol because the conversion of ethylene is low.

A liquid phase process using sulfuric acid has also been widely adopted for the hydration of propylene or butenes, industrially. However, in this process, a large quantity of energy is necessary for hydrolysis of a sulfuric acid ester once formed. Because of the concentration and regeneration of the diluted aqueous sulfuric acid solution, equipment may be violently corroded by the acid at high temperatures.

From equilibrium considerations, it is preferred that the hydration of olefins be carried out at a low temperature under a high pressure, and ordinarily, these reaction conditions provide high conversions of olefins to alcohols. However, it is necessary to obtain an industrially satisfactory rate of reaction, and practically, severe conditions of high temperatures and high pressures are adopted for obtaining such a high rate of reaction. For these reasons, it is desired to develop a highly active solid acid catalyst for the hydration of olefins, which is capable of reducing the consumption of energy and not causing corrosion of equipment or other trouble.

Attempts have been made to use solid catalysts for the hydration of olefins. For example, processes have been proposed using complex oxides composed of silica, alumina, zirconia, titanium oxide, molybdenum oxide and tungsten oxide, metal phosphates such as aluminum phosphate and zirconium phosphate, and crystalline aluminosilicates called “zeolites” such as mordenite and Y type zeolite. However, these catalysts possess a low activity and the activity is gradually degraded when the reaction is carried out at a high temperature.

As can be seen from the above discussion, previous methods rely on improving the catalysts used in the hydration reaction. Presently, little or no investigation has been done in improving mixing of the reactants e.g. olefins and water for improving and optimizing the reaction.

Consequently, there is a need for accelerated methods for making an alcohol by improving the mixing of olefins into the water phase.

SUMMARY

Methods and systems for the synthesis of alcohol are described herein. The methods and systems incorporate the novel use of a high shear device to promote dispersion and solubility of olefins in water. The high shear device may allow for lower reaction temperatures and pressures and may also reduce reaction time. Further advantages and aspects of the disclosed methods and system are described below.

In an embodiment, a method of making an alcohol comprises introducing an olefin into a water stream to form a gas-liquid stream. The method further comprises flowing the gas-liquid stream through a high shear device so as to form a dispersion with gas bubbles having a mean diameter less than about 1 micron. In addition, the method comprises contacting the gas-liquid stream with a catalyst in a reactor to hydrate the olefin gas and form an alcohol.

In an embodiment, a system for hydrating an olefin comprises at least one high shear device comprising a rotor and a stator. The rotor and the stator are separated by a shear gap in the range of from about 0.02 mm to about 5 mm. The shear gap is a minimum distance between the rotor and the stator. The high shear device is capable of producing a tip speed of the at least one rotor of greater than about 23 m/s (4,500 ft/min). In addition, the system comprises a pump configured for delivering a liquid stream comprising liquid phase to the high shear device. The system also comprises a reactor for hydrating an olefin coupled to the high shear device. The reactor is configured for receiving said dispersion from said high shear device.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram of a process for the making alcohol, according to certain embodiments of the invention.

FIG. 2 is a longitudinal cross-section view of a multi-stage high shear device, as employed in an embodiment of the system of FIG. 1.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claims to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”.

DETAILED DESCRIPTION

The disclosed methods and systems for the hydration of olefins employ a high shear mechanical device to provide rapid contact and mixing of the olefin gas and water in a controlled environment in the reactor/mixer device. The term “olefin gas” as used herein includes both substantially pure olefins as well as gaseous mixtures containing olefins. In particular, embodiments of the systems and methods may be used in the production of alcohols from the hydration of olefins. Preferably, the method comprises a heterogeneous phase reaction of liquid water with an olefin gas. The high shear device reduces the mass transfer limitations on the reaction and thus increases the overall reaction rate.

Chemical reactions involving liquids, gases and solids rely on time, temperature, and pressure to define the rate of reactions. In cases where it is desirable to react two or more raw materials of different phases (e.g. solid and liquid; liquid and gas; solid, liquid and gas), one of the limiting factors in controlling the rate of reaction involves the contact time of the reactants. In the case of heterogeneously catalyzed reactions there is the additional rate limiting factor of having the reacted products removed from the surface of the catalyst to enable the catalyst to catalyze further reactants. Contact time for the reactants and/or catalyst is often controlled by mixing which provides contact with two or more reactants involved in a chemical reaction. A reactor assembly that comprises an external high shear device or mixer as described herein makes possible decreased mass transfer limitations and thereby allows the reaction to more closely approach kinetic limitations. When reaction rates are accelerated, residence times may be decreased, thereby increasing obtainable throughput. Product yield may be increased as a result of the high shear system and process. Alternatively, if the product yield of an existing process is acceptable, decreasing the required residence time by incorporation of suitable high shear may allow for the use of lower temperatures and/or pressures than conventional processes.

System for Hydration Olefins. A high shear olefin hydration system will now be described in relation to FIG. 1, which is a process flow diagram of an embodiment of a high shear system 100 for the production of alcohols via the hydration of olefins. The basic components of a representative system include external high shear device (HSD) 140, vessel 110, and pump 105. As shown in FIG. 1, the high shear device may be located external to vessel/reactor 110. Each of these components is further described in more detail below. Line 121 is connected to pump 105 for introducing either an olefin reactant. Line 113 connects pump 105 to HSD 140, and line 118 connects HSD 140 to vessel 110. Line 122 is connected to line 113 for introducing an olefin gas. Line 117 is connected to vessel 110 for removal of unreacted olefins, and other reaction gases. Additional components or process steps may be incorporated between vessel 110 and HSD 140, or ahead of pump 105 or HSD 140, if desired. High shear devices (HSD) such as a high shear, or high shear mill, are generally divided into classes based upon their ability to mix fluids. Mixing is the process of reducing the size of inhomogeneous species or particles within the fluid. One metric for the degree or thoroughness of mixing is the energy density per unit volume that the mixing device generates to disrupt the fluid particles. The classes are distinguished based on delivered energy density. There are three classes of industrial mixers having sufficient energy density to consistently produce mixtures or emulsions with particle or bubble sizes in the range of 0 to 50 microns. High shear mechanical devices include homogenizers as well as colloid mills.]

High shear devices (HSD) such as a high shear, or high shear mill, are generally divided into classes based upon their ability to mix fluids. Mixing is the process of reducing the size of inhomogeneous species or particles within the fluid. One metric for the degree or thoroughness of mixing is the energy density per unit volume that the mixing device generates to disrupt the fluid particles. The classes are distinguished based on delivered energy density. There are three classes of industrial mixers having sufficient energy density to consistently produce mixtures or emulsions with particle or bubble sizes in the range of 0 to 50 μm.

Homogenization valve systems are typically classified as high energy devices. Fluid to be processed is pumped under very high pressure through a narrow-gap valve into a lower pressure environment. The pressure gradients across the valve and the resulting turbulence and cavitations act to break-up any particles in the fluid. These valve systems are most commonly used in milk homogenization and can yield average particle size range from about 0.01 μm to about 1 μm. At the other end of the spectrum are high shear systems classified as low energy devices. These systems usually have paddles or fluid rotors that turn at high speed in a reservoir of fluid to be processed, which in many of the more common applications is a food product. These systems are usually used when average particle, or bubble, sizes of greater than 20 microns are acceptable in the processed fluid.

Between low energy—high shears and homogenization valve systems, in terms of the mixing energy density delivered to the fluid, are colloid mills, which are classified as intermediate energy devices. The typical colloid mill configuration includes a conical or disk rotor that is separated from a complementary, liquid-cooled stator by a closely-controlled rotor-stator gap, which is maybe between 0.025 mm and 10.0 mm. Rotors are usually driven by an electric motor through a direct drive or belt mechanism. Many colloid mills, with proper adjustment, can achieve average particle, or bubble, sizes of about 0.01 μm to about 25 μm in the processed fluid. These capabilities render colloid mills appropriate for a variety of applications including colloid and oil/water-based emulsion processing such as that required for cosmetics, mayonnaise, silicone/silver amalgam formation, or roofing-tar mixing.

An approximation of energy input into the fluid (kW/L/min) can be made by measuring the motor energy (kW) and fluid output (L/min). In embodiments, the energy expenditure of a high shear device is greater than 1000 W/m³. In embodiments, the energy expenditure is in the range of from about 3000 W/m³ to about 7500 W/m³. The shear rate generated in a high shear device may be greater than 20,000 s⁻¹. In embodiments, the shear rate generated is in the range of from 20,000 s⁻¹ to 100,000 s⁻¹.

Tip speed is the velocity (m/sec) associated with the end of one or more revolving elements that is transmitting energy to the reactants. Tip speed, for a rotating element, is the circumferential distance traveled by the tip of the rotor per unit of time, and is generally defined by the equation V (m/sec)=π·D·n, where V is the tip speed, D is the diameter of the rotor, in meters, and n is the rotational speed of the rotor, in revolutions per second. Tip speed is thus a function of the rotor diameter and the rotation rate. Also, tip speed may be calculated by multiplying the circumferential distance transcribed by the rotor tip, 2πR, where R is the radius of the rotor (meters, for example) times the frequency of revolution (for example revolutions (meters, for example) times the frequency of revolution (for example revolutions per minute, rpm).

For colloid mills, typical tip speeds are in excess of 23 m/sec (4500 ft/min) and can exceed 40 m/sec (7900 ft/min). For the purpose of the present disclosure the term ‘high shear’ refers to mechanical rotor-stator devices, such as mills or mixers, that are capable of tip speeds in excess of 5 m/sec (1000 ft/min) and require an external mechanically driven power device to drive energy into the stream of products to be reacted. A high shear device combines high tip speeds with a very small shear gap to produce significant friction on the material being processed. Accordingly, a local pressure in the range of about 1000 MPa (about 145,000 psi) to about 1050 MPa (152,300 psi) and elevated temperatures at the tip of the shear mixer are produced during operation. In certain embodiments, the local pressure is at least about 1034 MPa (about 150,000 psi).

Referring now to FIG. 1, there is presented a schematic diagram of a high shear device 200. High shear device 200 comprises at least one rotor-stator combination. The rotor-stator combinations may also be known as generators 220, 230, 240 or stages without limitation. The high shear device 200 comprises at least two generators, and most preferably, the high shear device comprises at least three generators.

The first generator 220 comprises rotor 222 and stator 227. The second generator 230 comprises rotor 223, and stator 228; the third generator comprises rotor 224 and stator 229. For each generator 220, 230, 240 the rotor is rotatably driven by input 250. The generators 220, 230, 240 rotate about axis 260 in rotational direction 265. Stator 227 is fixably coupled to the high shear device wall 255.

The generators include gaps between the rotor and the stator. The first generator 220 comprises a first gap 225; the second generator 230 comprises a second gap 235; and the third generator 240 comprises a third gap 245. The gaps 225, 235, 245 are between about 0.025 mm (0.01 in) and 10.0 mm (0.4 in) wide. Alternatively, the process comprises utilization of a high shear device 200 wherein the gaps 225, 235, 245 are between about 0.5 mm (0.02 in) and about 2.5 mm (0.1 in). In certain instances the gap is maintained at about 1.5 mm (0.06 in). Alternatively, the gaps 225, 235, 245 are different between generators 220, 230, 240. In certain instances, the gap 225 for the first generator 220 is greater than about the gap 235 for the second generator 230, which is greater than about the gap 245 for the third generator 240.

Additionally, the width of the gaps 225, 235, 245 may comprise a coarse, medium, fine, and super-fine characterization. Rotors 222, 223, and 224 and stators 227, 228, and 229 may be toothed designs. Each generator may comprise two or more sets of rotor-stator teeth, as known in the art. Rotors 222, 223, and 224 may comprise a number of rotor teeth circumferentially spaced about the circumference of each rotor. Stators 227, 228, and 229 may comprise a number of stator teeth circumferentially spaced about the circumference of each stator. In embodiments, the inner diameter of the rotor is about 11.8 cm. In embodiments, the outer diameter of the stator is about 15.4 cm. In further embodiments, the rotor and stator may have alternate diameters in order to alter the tip speed and shear pressures. In certain embodiments, each of three stages is operated with a super-fine generator, comprising a gap of between about 0.025 mm and about 3 mm. When a feed stream 205 including solid particles is to be sent through high shear device 200, the appropriate gap width is first selected for an appropriate reduction in particle size and increase in particle surface area. In embodiments, this is beneficial for increasing catalyst surface area by shearing and dispersing the particles.

High shear device 200 is fed a reaction mixture comprising the feed stream 205. Feed stream 205 comprises an emulsion of the dispersible phase and the continuous phase. Emulsion refers to a liquefied mixture that contains two distinguishable substances (or phases) that will not readily mix and dissolve together. Most emulsions have a continuous phase (or matrix), which holds therein discontinuous droplets, bubbles, and/or particles of the other phase or substance. Emulsions may be highly viscous, such as slurries or pastes, or may be foams, with tiny gas bubbles suspended in a liquid. As used herein, the term “emulsion” encompasses continuous phases comprising gas bubbles, continuous phases comprising particles (e.g., solid catalyst), continuous phases comprising droplets of a fluid that is substantially insoluble in the continuous phase, and combinations thereof.

Feed stream 205 may include a particulate solid catalyst component. Feed stream 205 is pumped through the generators 220, 230, 240, such that product dispersion 210 is formed. In each generator, the rotors 222, 223, 224 rotate at high speed relative to the fixed stators 227, 228, 229. The rotation of the rotors pumps fluid, such as the feed stream 205, between the outer surface of the rotor 222 and the inner surface of the stator 227 creating a localized high shear condition. The gaps 225, 235, 245 generate high shear forces that process the feed stream 205. The high shear forces between the rotor and stator functions to process the feed stream 205 to create the product dispersion 210. Each generator 220, 230, 240 of the high shear device 200 has interchangeable rotor-stator combinations for producing a narrow distribution of the desired bubble size, if feedstream 205 comprises a gas, or globule size, if feedstream 205 comprises a liquid, in the product dispersion 210.

The product dispersion 210 of gas particles, or bubbles, in a liquid comprises an emulsion. In embodiments, the product dispersion 210 may comprise a dispersion of a previously immiscible or insoluble gas, liquid or solid into the continuous phase. The product dispersion 210 has an average gas particle, or bubble, size less than about 1.5 μm; preferably the bubbles are sub-micron in diameter. In certain instances, the average bubble size is in the range from about 1.0 μm to about 0.1 μm. Alternatively, the average bubble size is less than about 400 nm (0.4 μm) and most preferably less than about 100 nm (0.1 μm).

The high shear device 200 produces a gas emulsion capable of remaining dispersed at atmospheric pressure for at least about 15 minutes. For the purpose of this disclosure, an emulsion of gas particles, or bubbles, in the dispersed phase in product dispersion 210 that are less than 1.5 μm in diameter may comprise a micro-foam. Not to be limited by a specific theory, it is known in emulsion chemistry that sub-micron particles, or bubbles, dispersed in a liquid undergo movement primarily through Brownian motion effects. The bubbles in the emulsion of product dispersion 210 created by the high shear device 200 may have greater mobility through boundary layers of solid catalyst particles, thereby facilitating and accelerating the catalytic reaction through enhanced transport of reactants.

The rotor is set to rotate at a speed commensurate with the diameter of the rotor and the desired tip speed as described hereinabove. Transport resistance is reduced by incorporation of high shear device 200 such that the velocity of the reaction is increased by at least about 5%. Alternatively, the high shear device 200 comprises a high shear colloid mill that serves as an accelerated rate reactor (ARR). The accelerated rate reactor comprises a single stage dispersing chamber. The accelerated rate reactor comprises a multiple stage inline disperser comprising at least 2 stages.

Selection of the high shear device 200 is dependent on throughput requirements and desired particle or bubble size in the outlet dispersion 210. In certain instances, high shear device 200 comprises a Dispax Reactor® of IKA® Works, Inc. Wilmington, N.C. and APV North America, Inc. Wilmington, Mass. Model DR 2000/4, for example, comprises a belt drive, 4M generator, PTFE sealing ring, inlet flange 1″ sanitary clamp, outlet flange ¾″ sanitary clamp, 2HP power, output speed of 7900 rpm, flow capacity (water) approximately 300 l/h to approximately 700 l/h (depending on generator), a tip speed of from 9.4 m/s to about 41 m/s (about 1850 ft/min to about 8070 ft/min). Several alternative models are available having various inlet/outlet connections, horsepower, nominal tip speeds, output rpm, and nominal flow rate.

Without wishing to be limited to a particular theory, it is believed that the level or degree of high shear is sufficient to increase rates of mass transfer and may also produce localized non-ideal conditions that enable reactions to occur that would not otherwise be expected to occur based on Gibbs free energy predictions. Localized non ideal conditions are believed to occur within the high shear device resulting in increased temperatures and pressures with the most significant increase believed to be in localized pressures. The increase in pressures and temperatures within the high shear device are instantaneous and localized and quickly revert back to bulk or average system conditions once exiting the high shear device. In some cases, the high shear device induces cavitation of sufficient intensity to dissociate one or more of the reactants into free radicals, which may intensify a chemical reaction or allow a reaction to take place at less stringent conditions than might otherwise be required. Cavitation may also increase rates of transport processes by producing local turbulence and liquid micro-circulation (acoustic streaming).

Vessel. Vessel or reactor 110 is any type of vessel in which a multiphase reaction can be propagated to carry out the above-described conversion reaction(s). For instance, a continuous or semi-continuous stirred tank reactor, or one or more batch reactors may be employed in series or in parallel. In some applications vessel 110 may be a tower reactor, and in others a tubular reactor or multi-tubular reactor. A catalyst inlet line 115 may be connected to vessel 110 for receiving a catalyst solution or slurry during operation of the system.

Vessel 110 may include one or more of the following components: stirring system, heating and/or cooling capabilities, pressure measurement instrumentation, temperature measurement instrumentation, one or more injection points, and level regulator (not shown), as are known in the art of reaction vessel design. For example, a stirring system may include a motor driven mixer. A heating and/or cooling apparatus may comprise, for example, a heat exchanger. Alternatively, as much of the conversion reaction may occur within HSD 140 in some embodiments, vessel 110 may serve primarily as a storage vessel in some cases. Although generally less desired, in some applications vessel 110 may be omitted, particularly if multiple high shears/reactors are employed in series, as further described below.

Heat Transfer Devices. In addition to the above-mentioned heating/cooling capabilities of vessel 110, other external or internal heat transfer devices for heating or cooling a process stream are also contemplated in variations of the embodiments illustrated in FIG. 1. Some suitable locations for one or more such heat transfer devices are between pump 105 and HSD 140, between HSD 140 and vessel 110, and between vessel 110 and pump 105 when system 1 is operated in multi-pass mode. Some non-limiting examples of such heat transfer devices are shell, tube, plate, and coil heat exchangers, as are known in the art.

Pumps. Pump 105 is configured for either continuous or semi-continuous operation, and may be any suitable pumping device that is capable of providing greater than 2 atm pressure, preferably greater than 3 atm pressure, to allow controlled flow through HSD 140 and system 1. For example, a Roper Type 1 gear pump, Roper Pump Company (Commerce Georgia) Dayton Pressure Booster Pump Model 2P372E, Dayton Electric Co (Niles, Ill.) is one suitable pump. Preferably, all contact parts of the pump comprise stainless steel. In some embodiments of the system, pump 105 is capable of pressures greater than about 20 atm. In addition to pump 105, one or more additional, high pressure pump (not shown) may be included in the system illustrated in FIG. 1. For example, a booster pump, which may be similar to pump 105, may be included between HSD 140 and vessel 110 for boosting the pressure into vessel 110. As another example, a supplemental feed pump, which may be similar to pump 105, may be included for introducing additional reactants or catalyst into vessel 110.

Hydration of Olefins. In operation for the catalytic hydration of olefins, respectively, a dispersible olefin gas stream is introduced into system 100 via line 122, and combined in line 113 with a water stream to form a gas-liquid stream. Alternatively, the olefin gas may be fed directly into HSD 140, instead of being combined with the liquid reactant (i.e., water) in line 113. Pump 105 is operated to pump the liquid reactant (water) through line 121, and to build pressure and feed HSD 140, providing a controlled flow throughout high shear (HSD) 140 and high shear system 100.

In a preferred embodiment, olefin gas may continuously be fed into the water stream 112 to form high shear feed stream 113 (e.g. a gas-liquid stream). In high shear device 140, water and the olefin vapor are highly dispersed such that nanobubbles and/or microbubbles of olefin are formed for superior dissolution of olefin vapor into solution. Once dispersed, the dispersion may exit high shear device 140 at high shear outlet line 118. Stream 118 may optionally enter fluidized or fixed bed 142 in lieu of a slurry catalyst process. However, in a slurry catalyst embodiment, high shear outlet stream 118 may directly enter hydration reactor 110 for hydration. The reaction stream may be maintained at the specified reaction temperature, using cooling coils in the reactor 110 to maintain reaction temperature. Hydration products (e.g. alcohols) may be withdrawn at product stream 116.

In an exemplary embodiment, the high shear device comprises a commercial disperser such as IKA® model DR 2000/4, a high shear, three stage dispersing device configured with three rotors in combination with stators, aligned in series. The disperser is used to create the dispersion of olefins in the liquid medium comprising water (i.e., “the reactants”). The rotor/stator sets may be configured as illustrated in FIG. 2, for example. The combined reactants enter the high shear device via line 113 and enter a first stage rotor/stator combination having circumferentially spaced first stage shear openings. The coarse dispersion exiting the first stage enters the second rotor/stator stage, which has second stage shear openings. The reduced bubble-size dispersion emerging from the second stage enters the third stage rotor/stator combination having third stage shear openings. The dispersion exits the high shear device via line 118. In some embodiments, the shear rate increases stepwise longitudinally along the direction of the flow. For example, in some embodiments, the shear rate in the first rotor/stator stage is greater than the shear rate in subsequent stage(s). In other embodiments, the shear rate is substantially constant along the direction of the flow, with the stage or stages being the same. If the high shear device includes a PTFE seal, for example, the seal may be cooled using any suitable technique that is known in the art. For example, the reactant stream flowing in line 113 may be used to cool the seal and in so doing be preheated as desired prior to entering the high shear device.

The rotor of HSD 140 is set to rotate at a speed commensurate with the diameter of the rotor and the desired tip speed. As described above, the high shear device (e.g., colloid mill) has either a fixed clearance between the stator and rotor or has adjustable clearance. HSD 140 serves to intimately mix the olefin vapor and the reactant liquid (i.e., water). In some embodiments of the process, the transport resistance of the reactants is reduced by operation of the high shear device such that the velocity of the reaction (i.e. reaction rate) is increased by greater than a factor of about 5. In some embodiments, the velocity of the reaction is increased by at least a factor of 10. In some embodiments, the velocity is increased by a factor in the range of about 10 to about 100 fold. In some embodiments, HSD 140 delivers at least 300 L/h with a power consumption of 1.5 kW at a nominal tip speed of at least 4500 ft/min, and which may exceed 7900 ft/min (140 m/sec). Although measurement of instantaneous temperature and pressure at the tip of a rotating shear unit or revolving element in HSD 140 is difficult, it is estimated that the localized temperature seen by the intimately mixed reactants may be in excess of 500° C. and at pressures in excess of 500 kg/cm² under high shear conditions. The high shear results in dispersion of the olefin gas in micron or submicron-sized bubbles. In some embodiments, the resultant dispersion has an average bubble size less than about 1.5 μm. Accordingly, the dispersion exiting HSD 140 via line 118 comprises micron and/or submicron-sized gas bubbles. In some embodiments, the mean bubble size is in the range of about 0.4 μm to about 1.5 μm. In some embodiments, the mean bubble size is less than about 400 nm, and may be about 100 nm in some cases. In many embodiments, the microbubble dispersion is able to remain dispersed at atmospheric pressure for at least 15 minutes.

Once dispersed, the resulting olefin/water dispersion exits HSD 140 via line 118 and feeds into vessel 110, as illustrated in FIG. 1. As a result of the intimate mixing of the reactants prior to entering vessel 110, a significant portion of the chemical reaction may take place in HSD 140, with or without the presence of a catalyst. Accordingly, in some embodiments, reactor/vessel 110 may be used primarily for heating and separation of volatile reaction products from the alcohol product. Alternatively, or additionally, vessel 110 may serve as a primary reaction vessel where most of the alcohol product is produced. Vessel/reactor 110 may be operated in either continuous or semi-continuous flow mode, or it may be operated in batch mode. The contents of vessel 110 may be maintained at a specified reaction temperature using heating and/or cooling capabilities (e.g., cooling coils) and temperature measurement instrumentation. Pressure in the vessel may be monitored using suitable pressure measurement instrumentation, and the level of reactants in the vessel may be controlled using a level regulator (not shown), employing techniques that are known to those of skill in the art. The contents are stirred continuously or semi-continuously.

Commonly known hydration reaction conditions may suitably be employed as the conditions of the production of an alcohol by hydrating olefins by using catalysts. There is no particular restriction as to the reaction conditions. The hydration reaction of an olefin is an equilibrium reaction to the reverse reaction, that is, the dehydration reaction of an alcohol, and a low temperature and a high pressure are ordinarily advantageous for the formation of an alcohol. However, preferred conditions greatly differ according to the particular starting olefin. From the viewpoint of the rate of reaction, a higher temperature is preferred. Accordingly, it is difficult to simply define the reaction conditions. However, in embodiments, a reaction temperature may range from about 50° C. to about 350° C., preferably from about 100° C. to about 300° C. Furthermore, the reaction pressure may range from about 1 to 300 atmospheres, alternatively 1 to 250 atmospheres.

The process according can be carried out under substantially the same conditions as those employed in the hitherto known direct hydration processes; however, in the process according to the invention it is both possible and advantageous for the molar ratio of water to olefin in the charge to be very low. A molar ratio of water to olefin considerably higher than would correspond to the ratio in the charge may, however, occur in the reactor, since only a portion of the liquid water supplied together with the charge is converted in the sump of the reactor and withdrawn together with the stream of vaporous product. Accordingly, a considerably molar excess of water (or of an aqueous acid solution) may be kept constantly available in the sump of the reactor in the process of the invention, a high selectivity of the hydration reaction for alcohol being thus ensured. It is generally sufficient for the charge to the reactor to contain about from 1 to 1.5 moles of liquid water per mole of converted olefin. Nevertheless, a molar ratio of water to olefin of from 15 to 30 or higher depending upon the required selectivity of the hydration process for the formation of alcohol may be adjusted without having to make allowance for the disadvantages involved in an elaborate recovery of the crude product from the aqueous phase.

The olefins for the reaction may be used alone or in combination as a mixture of different types. The olefins can have any structure, such as, aliphatic, aromatic, heteroaromatic, aliphatic-aromatic or aliphatic-heteroaromatic. They can also contain other functional groups, and it should be determined beforehand whether these functional groups should remain unchanged or should be hydrated themselves.

Embodiments of the disclosed process may be suitable for hydrating straight or branched olefins. The described process may be used for hydrating a wide variety of straight or branched chain olefins containing from 2 to 8 carbon atoms.

Catalyst. If a catalyst is used to promote the hydration reaction, it may be introduced into the vessel via line 115, as an aqueous or nonaqueous slurry or stream. Alternatively, or additionally, catalyst may be added elsewhere in the system 100. For example, catalyst slurry may be injected into line 121. In some embodiments, line 121 may contain a flowing water stream and/or olefin recycle stream from vessel 110.

In embodiments, any catalyst suitable for catalyzing a hydration reaction may be employed. An inert gas such as nitrogen may be used to fill reactor 110 and purge it of any air and/or oxygen. According to one embodiment, the catalyst is phosphoric acid disposed on a solid support such as without limitation, silica. In other embodiments, the catalyst may be sulfuric acid or sulfonic acid. Furthermore, the catalyst may comprise a zeolite. Examples of the zeolites usable in various embodiments include crystalline aluminosilicates such as mordenite, erionite, ferrierite and ZSM zeolites developed by Mobil Oil Corp.; aluminometallosilicates containing foreign elements such as boron, iron, gallium, titanium, copper, silver, etc.; and metallosilicates substantially free of aluminum, such as gallosilicates and borosilicates. As regards the cationic species which are exchangeable in the zeolites, the proton-exchanged type (H-type) zeolites are usually used, but it is also possible to use the zeolites which have been ion-exchanged with at least one cationic species, for example, an alkaline earth element such as Mg, Ca and Sr, a rare earth element such as La and Ce, a VIII-group element such as Fe, Co, Ni, Ru, Pd and Pt, or other element such as Ti, Zr, Hf, Cr, Mo, W and Th. Catalyst may be fed into reactor 110 through catalyst feed stream 115. Alternatively, catalyst may be present in a fixed or fluidized bed 142.

The bulk or global operating temperature of the reactants is desirably maintained below their flash points. In some embodiments, the operating conditions of system 100 comprise a temperature in the range of from about 50° C. to about 300° C. In specific embodiments, the reaction temperature in vessel 110, in particular, is in the range of from about 90° C. to about 220° C. In some embodiments, the reaction pressure in vessel 110 is in the range of from about 5 atm to about 50 atm.

The dispersion may be further processed prior to entering vessel 110 (as indicated by arrow 18), if desired. In vessel 110, olefin hydration occurs via catalytic hydration. The contents of the vessel are stirred continuously or semi-continuously, the temperature of the reactants is controlled (e.g., using a heat exchanger), and the fluid level inside vessel 110 is regulated using standard techniques. Olefin hydration may occur either continuously, semi-continuously or batch wise, as desired for a particular application. Any reaction gas that is produced exits reactor 110 via gas line 117. This gas stream may comprise unreacted olefins, for example. The reaction gas removed via line 117 may be further treated, and the components may be recycled, as desired.

The reaction product stream including unconverted olefins and corresponding byproducts exits vessel 110 by way of line 116. The alcohol product may be recovered and treated as known to those of skill in the art.

Multiple Pass Operation. In the embodiment shown in FIG. 1, the system is configured for single pass operation, wherein the output from vessel 110 goes directly to further processing for recovery of alcohol product. In some embodiments it may be desirable to pass the contents of vessel 110, or a liquid fraction containing unreacted olefin, through HSD 140 during a second pass. In this case, line 116 is connected to line 121 via dotted line 120, and the recycle stream from vessel 110 is pumped by pump 105 into line 113 and thence into HSD 140. Additional olefin gas may be injected via line 122 into line 113, or it may be added directly into the high shear device (not shown).

Multiple High shear Devices. In some embodiments, two or more high shear devices like HSD 140, or configured differently, are aligned in series, and are used to further enhance the reaction. Their operation may be in either batch or continuous mode. In some instances in which a single pass or “once through” process is desired, the use of multiple high shear devices in series may also be advantageous. In some embodiments where multiple high shear devices are operated in series, vessel 110 may be omitted. In some embodiments, multiple high shear devices 140 are operated in parallel, and the outlet dispersions therefrom are introduced into one or more vessel 110.

While embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations. Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, and the like. Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every original claim is incorporated into the specification as an embodiment of the invention. Thus, the claims are a further description and are an addition to the preferred embodiments of the present invention. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent they provide exemplary, procedural or other details supplementary to those set forth herein. 

1. A method of hydrating an olefin comprising: a) introducing an olefin gas into a high shear device; b) introducing a water stream into said high shear device; c) forming a dispersion in the high shear device comprising gas bubbles having a mean diameter of less than about 1 micron; and d) contacting the dispersion with a catalyst in a reactor to hydrate the olefin gas and form an alcohol.
 2. The method of claim 1, wherein the gas bubbles have an average diameter of no more than about 400 nm.
 3. The method of claim 1, wherein the olefin gas comprises one or more olefins comprising from 2 to 8 carbon atoms.
 4. The method of claim 1, wherein the water stream includes a liquid-gas stream formed by mixing a second olefin gas stream with water.
 5. The method of claim 1, wherein (c) comprises subjecting said olefin gas and water to high shear mixing at a tip speed of at least about 23 m/sec.
 6. The method of claim 1, wherein (c) comprises subjecting said olefin gas and water to a shear rate of greater than about 20,000 s⁻¹.
 7. The method of claim 1, wherein forming said dispersion comprises an energy expenditure of at least about 1000 W/m³.
 8. The method of claim 1 further comprising introducing the dispersion to a fixed bed containing a catalyst.
 9. The method of claim 1 further comprising mixing the catalyst with the water stream to form a slurry before (b).
 10. The method of claim 1, wherein the catalyst is selected from the group consisting of phosphoric acid, sulfonic acid, sulfuric acid, a zeolite, and combinations thereof.
 11. The method of claim 1, wherein the alcohol is selected from the group consisting of ethanol, isopropanol, butanol, propanol, and combinations thereof.
 12. The method of claim 1, wherein said high shear device comprises a rotor and a stator separated by a shear gap in the range of from about 0.02 mm to about 5 mm, wherein the shear gap is a minimum distance between said rotor and said stator.
 13. The method of claim 1, wherein the high shear device comprises two or more rotors and two or more stators.
 14. The method of claim 1, wherein said high shear device comprises a rotor tip, and said device is configured for operating at a flow rate of at least 300 L/h at a tip speed of at least about 23 m/sec.
 15. The method of claim 1, wherein said high shear device is configured for operating at a tip speed of at least 40 m/sec.
 16. The method of claim 1 comprising utilizing more than one high shear device.
 17. The method of claim 1, wherein the high shear device comprises at least two generators.
 18. The method of claim 17, wherein the shear rate provided by one generator is greater than the shear rate provided by another generator.
 19. The method of claim 1 wherein said reactor is a fixed bed reactor.
 20. The method of claim 1 wherein said reactor comprises a hydration catalyst. 